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Drosophila melanogaster Cad99C, the orthologue of human Usher cadherin PCDH15, regulates the length of microvilli.

D'Alterio C, Tran DD, Yeung MW, Hwang MS, Li MA, Arana CJ, Mulligan VK, Kubesh M, Sharma P, Chase M, Tepass U, Godt D - J. Cell Biol. (2005)

Bottom Line: Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length.Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length.This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5.

ABSTRACT
Actin-based protrusions can form prominent structures on the apical surface of epithelial cells, such as microvilli. Several cytoplasmic factors have been identified that control the dynamics of actin filaments in microvilli. However, it remains unclear whether the plasma membrane participates actively in microvillus formation. In this paper, we analyze the function of Drosophila melanogaster cadherin Cad99C in the microvilli of ovarian follicle cells. Cad99C contributes to eggshell formation and female fertility and is expressed in follicle cells, which produce the eggshells. Cad99C specifically localizes to apical microvilli. Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length. Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length. This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

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Cad99C localizes to the apical microvilli of follicle cells. Cad99C is always red. Confocal images of the follicular epithelium are from egg chambers at stage 10 in A–F or the indicated stage in G–L. Nomarski images are shown in panels marked with ‘ or “. (A and B) Cad99C is located apical to the adherens junction marker DE-cadherin (DEcad) and the apical cortex marker DPatj of follicle cells. Bars, 10 μm. (C) Cad99C distribution does not overlap with the oocyte cortex marker Yolkless (Yl). Bar, 10 μm. (D) Apical microvilli of follicle cells can be seen individually at stage 10a. Bar, 5 μm. (E) The pattern of Cad99C positive microvilli reflects the hexagonal array of follicle cells in a top view. Bar, 10 μm. (F–F”) Cad99C colocalizes with the apical CD8::GPF staining in follicle cells. CD8::GFP, which is expressed only in follicle cells using da-Gal4 as a driver, outlines all plasma membrane structures of follicle cells, including the apical microvillus brush border. Bar, 10 μm. (G–J) Cad99C staining reflects the dynamic changes in microvillus length: a strong growth from stage 9 (G) to late 10a (H), and a progressive shortening from stage 10b (I) to stage 11 (J). Bars, 10 μm. (K–K”) The microvillus brush border of follicle cells forms a distinct band in a Nomarski image (K’). The stripe pattern of this band reflects the alternate arrangement of microvilli and vitelline bodies at stage 10 of oogenesis. Bar, 10 μm. (L–L”) At stage 12, follicle cell microvilli are much shorter than at stage 10 and the vitelline bodies have fused into a layer, the VM. Bar, 10 μm. The apical surface of follicle cells, which faces the overlying oocyte, is marked by an arrowhead in A–C, F, G, K, and L. Oc, oocyte; Fc, follicle cells; MV, microvilli; VB, vitelline bodies.
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fig4: Cad99C localizes to the apical microvilli of follicle cells. Cad99C is always red. Confocal images of the follicular epithelium are from egg chambers at stage 10 in A–F or the indicated stage in G–L. Nomarski images are shown in panels marked with ‘ or “. (A and B) Cad99C is located apical to the adherens junction marker DE-cadherin (DEcad) and the apical cortex marker DPatj of follicle cells. Bars, 10 μm. (C) Cad99C distribution does not overlap with the oocyte cortex marker Yolkless (Yl). Bar, 10 μm. (D) Apical microvilli of follicle cells can be seen individually at stage 10a. Bar, 5 μm. (E) The pattern of Cad99C positive microvilli reflects the hexagonal array of follicle cells in a top view. Bar, 10 μm. (F–F”) Cad99C colocalizes with the apical CD8::GPF staining in follicle cells. CD8::GFP, which is expressed only in follicle cells using da-Gal4 as a driver, outlines all plasma membrane structures of follicle cells, including the apical microvillus brush border. Bar, 10 μm. (G–J) Cad99C staining reflects the dynamic changes in microvillus length: a strong growth from stage 9 (G) to late 10a (H), and a progressive shortening from stage 10b (I) to stage 11 (J). Bars, 10 μm. (K–K”) The microvillus brush border of follicle cells forms a distinct band in a Nomarski image (K’). The stripe pattern of this band reflects the alternate arrangement of microvilli and vitelline bodies at stage 10 of oogenesis. Bar, 10 μm. (L–L”) At stage 12, follicle cell microvilli are much shorter than at stage 10 and the vitelline bodies have fused into a layer, the VM. Bar, 10 μm. The apical surface of follicle cells, which faces the overlying oocyte, is marked by an arrowhead in A–C, F, G, K, and L. Oc, oocyte; Fc, follicle cells; MV, microvilli; VB, vitelline bodies.

Mentions: To address the function of Cad99C in the follicular epithelium, we first examined the subcellular localization of this cadherin and found that it is confined to the apical microvillus brush border. Cad99C is located apical to DE-cadherin (Fig. 4 A) and DPatj (Fig. 4 B), which mark the adherens junctions and apical cell cortex, respectively (Oda et al., 1994; Tanentzapf et al., 2000). In contrast to DE-cadherin, Cad99C is not seen at the apicolateral and lateral plasma membrane, where follicle cells are in contact with one another. Cad99C shows a spiky pattern in a side view (Fig. 4, A and D) and a carpetlike pattern in a front view of the apical cell surface (Fig. 4 E), which is consistent with a localization to microvilli. Several observations support that Cad99C is specific for follicle cell microvilli and not found in oocyte microvilli, with which they make contact. First, Cad99C expression was not detected in the germline (Fig. 1, A–F). Second, the pattern of Cad99C-positive microvilli reflects the honeycomb pattern of follicle cells (Fig. 4 E), whereas oocyte microvilli form a continuous lawn (Mahowald and Kambysellis, 1980). Third, Cad99C does not overlap with Yolkless, a marker that labels the oocyte cortex (Fig. 4 C; Schönbaum et al., 2000) but colocalizes with a marker specifically expressed in follicle cells (CD8-GFP; Fig. 4 F). We infer that Cad99C does not mediate homophilic adhesion between follicle cells or between microvilli of follicle cells and those of the oocyte.


Drosophila melanogaster Cad99C, the orthologue of human Usher cadherin PCDH15, regulates the length of microvilli.

D'Alterio C, Tran DD, Yeung MW, Hwang MS, Li MA, Arana CJ, Mulligan VK, Kubesh M, Sharma P, Chase M, Tepass U, Godt D - J. Cell Biol. (2005)

Cad99C localizes to the apical microvilli of follicle cells. Cad99C is always red. Confocal images of the follicular epithelium are from egg chambers at stage 10 in A–F or the indicated stage in G–L. Nomarski images are shown in panels marked with ‘ or “. (A and B) Cad99C is located apical to the adherens junction marker DE-cadherin (DEcad) and the apical cortex marker DPatj of follicle cells. Bars, 10 μm. (C) Cad99C distribution does not overlap with the oocyte cortex marker Yolkless (Yl). Bar, 10 μm. (D) Apical microvilli of follicle cells can be seen individually at stage 10a. Bar, 5 μm. (E) The pattern of Cad99C positive microvilli reflects the hexagonal array of follicle cells in a top view. Bar, 10 μm. (F–F”) Cad99C colocalizes with the apical CD8::GPF staining in follicle cells. CD8::GFP, which is expressed only in follicle cells using da-Gal4 as a driver, outlines all plasma membrane structures of follicle cells, including the apical microvillus brush border. Bar, 10 μm. (G–J) Cad99C staining reflects the dynamic changes in microvillus length: a strong growth from stage 9 (G) to late 10a (H), and a progressive shortening from stage 10b (I) to stage 11 (J). Bars, 10 μm. (K–K”) The microvillus brush border of follicle cells forms a distinct band in a Nomarski image (K’). The stripe pattern of this band reflects the alternate arrangement of microvilli and vitelline bodies at stage 10 of oogenesis. Bar, 10 μm. (L–L”) At stage 12, follicle cell microvilli are much shorter than at stage 10 and the vitelline bodies have fused into a layer, the VM. Bar, 10 μm. The apical surface of follicle cells, which faces the overlying oocyte, is marked by an arrowhead in A–C, F, G, K, and L. Oc, oocyte; Fc, follicle cells; MV, microvilli; VB, vitelline bodies.
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fig4: Cad99C localizes to the apical microvilli of follicle cells. Cad99C is always red. Confocal images of the follicular epithelium are from egg chambers at stage 10 in A–F or the indicated stage in G–L. Nomarski images are shown in panels marked with ‘ or “. (A and B) Cad99C is located apical to the adherens junction marker DE-cadherin (DEcad) and the apical cortex marker DPatj of follicle cells. Bars, 10 μm. (C) Cad99C distribution does not overlap with the oocyte cortex marker Yolkless (Yl). Bar, 10 μm. (D) Apical microvilli of follicle cells can be seen individually at stage 10a. Bar, 5 μm. (E) The pattern of Cad99C positive microvilli reflects the hexagonal array of follicle cells in a top view. Bar, 10 μm. (F–F”) Cad99C colocalizes with the apical CD8::GPF staining in follicle cells. CD8::GFP, which is expressed only in follicle cells using da-Gal4 as a driver, outlines all plasma membrane structures of follicle cells, including the apical microvillus brush border. Bar, 10 μm. (G–J) Cad99C staining reflects the dynamic changes in microvillus length: a strong growth from stage 9 (G) to late 10a (H), and a progressive shortening from stage 10b (I) to stage 11 (J). Bars, 10 μm. (K–K”) The microvillus brush border of follicle cells forms a distinct band in a Nomarski image (K’). The stripe pattern of this band reflects the alternate arrangement of microvilli and vitelline bodies at stage 10 of oogenesis. Bar, 10 μm. (L–L”) At stage 12, follicle cell microvilli are much shorter than at stage 10 and the vitelline bodies have fused into a layer, the VM. Bar, 10 μm. The apical surface of follicle cells, which faces the overlying oocyte, is marked by an arrowhead in A–C, F, G, K, and L. Oc, oocyte; Fc, follicle cells; MV, microvilli; VB, vitelline bodies.
Mentions: To address the function of Cad99C in the follicular epithelium, we first examined the subcellular localization of this cadherin and found that it is confined to the apical microvillus brush border. Cad99C is located apical to DE-cadherin (Fig. 4 A) and DPatj (Fig. 4 B), which mark the adherens junctions and apical cell cortex, respectively (Oda et al., 1994; Tanentzapf et al., 2000). In contrast to DE-cadherin, Cad99C is not seen at the apicolateral and lateral plasma membrane, where follicle cells are in contact with one another. Cad99C shows a spiky pattern in a side view (Fig. 4, A and D) and a carpetlike pattern in a front view of the apical cell surface (Fig. 4 E), which is consistent with a localization to microvilli. Several observations support that Cad99C is specific for follicle cell microvilli and not found in oocyte microvilli, with which they make contact. First, Cad99C expression was not detected in the germline (Fig. 1, A–F). Second, the pattern of Cad99C-positive microvilli reflects the honeycomb pattern of follicle cells (Fig. 4 E), whereas oocyte microvilli form a continuous lawn (Mahowald and Kambysellis, 1980). Third, Cad99C does not overlap with Yolkless, a marker that labels the oocyte cortex (Fig. 4 C; Schönbaum et al., 2000) but colocalizes with a marker specifically expressed in follicle cells (CD8-GFP; Fig. 4 F). We infer that Cad99C does not mediate homophilic adhesion between follicle cells or between microvilli of follicle cells and those of the oocyte.

Bottom Line: Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length.Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length.This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5.

ABSTRACT
Actin-based protrusions can form prominent structures on the apical surface of epithelial cells, such as microvilli. Several cytoplasmic factors have been identified that control the dynamics of actin filaments in microvilli. However, it remains unclear whether the plasma membrane participates actively in microvillus formation. In this paper, we analyze the function of Drosophila melanogaster cadherin Cad99C in the microvilli of ovarian follicle cells. Cad99C contributes to eggshell formation and female fertility and is expressed in follicle cells, which produce the eggshells. Cad99C specifically localizes to apical microvilli. Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length. Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length. This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

Show MeSH
Related in: MedlinePlus